Safety plug and lamp socket



July 3, '1928.

L. KELLNER SAFETY PLUG AND LAMP SOCKET Filed May 16, 1925 lN-VENTOR Lows` Kell/7er ATTORNEY 6 Patented YJuly 3, 1928.

,mais KELLNEB, QF passes?, 114.1311915.

`sar-rrr .PLUG `AND man enfriar;

Appneetien mear/ray is, 1925. semi ne. aegee The main object of this yinvention is to provide a 1plug adapted to be screwed into "the ordinary lamp socket andto `form in said a terminal socket adapted to receive the ordinary-standard threaded terminal cap of an 4inc andescent electric light bulb; and to' so construct thesaid plug andjsocket that the plug will be locked in the ordinary stand- "ard lamp socket and the lamp will be locked inthe terminal socket, as described. The 'oijtlinary .eleetric lamp bulb` may be used in connection with thcordinary `lamp socket, it Vbeing' onlynecessary to `interpose my safety plug and sockegconnectingthe plug to the ordinary standard lamp `socket andscrewing the lamp inthe terminal socket ofthe plug. Another `object of the invention is to provide removable means in the torni of a key `for locking theiseveralparts ofthe safety plugandsocket together so` that the lamp may' beunscrewed therefrom, or the plug ndisocket ina be unscrewed from the standard lamp soc tet.

lhile I have shown and described my invention` used in connectionjwith an electric light bulb; it is manifest' that it may be used. `Withyany ,form of electrical connection, car- "ryingterminal wires and adaptedvto have a threaded engagement Witha socket having `c.oinplementary contacts and terminals.`

`f yIn the drawing Fig. l isa side elevation of anlincandescent electric light bulb in positionin the plug and socket,"the 'plug and socketbeingshownin longitudinal.sectional K y y Y l terminal shell andloosely A1s an externallythreaded connector sleeve View; e l Y Fig..2 aside elevation of the connector sleeve; e l Fig a. side elevation ,o the terminal shell showing the insulating `plug therein;

Fig. l afdetail View ofthe removable key fr locking the rotatable parts of the plug and socket together' i" p Fig. 5 a detail view of theretainjng ring for holding thevarionspartsassembled;

6 a side elevation of the insulating retainer and guard; yand Fig. 7 a plan view of said guard. y Referring .to thev various parts lby numerals, l designates ya terminal shell which is "formed of metal, preferably ofhrass. rl `his terminal shell fissubstantially cylindrical at one endlas AatZ and in :this endis4 rigidly :se-

VCured va plu 3 of insulation, vsaid plug `projeoting slig itly beyond the free end mf` the cyflindricalpart ot' the `tsvzrminal shell. `The 'other end df the terminal shell is slightly enlarged in diameter and 4:is internally threaded to form a terminal socketfl. rlhe free end ofthe socket portion ofi" the Ashell iis expanded to form the outwardly extending -inelined lflocking flange 5.

The lug .is

held in} place Within the endvnQ of tie shell l byjha'venig its outer end engaged b lan Ainturned llunge -6 formed-'on the ent of the shell and i'tsinner end engaged by an aning SWhich extends `longitudinallly and centrally therethrough,` the said opening being reduced in si` ze` inner' end.` VA contact pin als. slldably mounted atts lower" end Within the opening 8 and disposed within Athe opening'below the pin f) andconnected theretoisa coiled sprinfr 10. The lower end ci the spring t10 leateries throughtheieinner 'restricted-end 4of'theopeningT8 andhas a `contact `11 connected thereto,` said contact fiestsdiigectly on the yinner `end of theplug 3 ,andfis preferably slightly `yieldable and is arranged'in position to be engaged bythe 'a shoulder-l2. y p

"Surrounding the pluer `portion y2 of Vthe rotatable thereon sleeve "being threaded to adapt it to screw into the ordinary standard threaded `lampsocket orplug receptacle. The connectorI sleeve extends vbeyond the outer end of `the "shell and atflt's inner end it is fformelyvith rthe enlarged annular lockllange or'skirt lll.` This flange extends toa point `eadjacent `theftlard".end 5 of the terminal shell 1 and iswconnected to thevlhody portion ofthe sleeve 513 by a radial shoulder portion l5. Thefshoulderfportion 15 `of the connector sleeve `fits `close to the corresponding .shoulder 12 o n the terminal.she-lllv `A tub Alar guard and opera-ting sleeve Nl16 off-'insulating niaterialencloses'the socket end licfthe ythellange la of nular rib f7 `formedby crinipilngthe shellin- Wardly v*The plug v3 is formed withan openthe connector sleeve. An internal annular' groove 17 is formed in one end of the guard and into said groove a split, resilient, re taining ring 18 is snapped. This retalning ring tits over the outer surface of the shoulder 15 of the connector sleeve and thereby locks the connector sleeve to the guard against longitudinal movement but the connector sleeve and guard may be freely rotated independently of each other. The end of the tubular guard, adjacent the eX- panded end of the terminal socket 4, is formed with an inwardly extending annular stop flange 19 which is adapted to engage the lock flange 5 of the terminal shell. The stop fiange 19 cooperates` with the locking fiange 5 of the terminal shell and with the lock ring 18 to lock the guard in position andhold it against.longitudinal movement. The tubular guard and the connector sleeve are freely rotatable independently of each other; and when the connector sleeve 1s screwed into a socket, the terminal shell is freely rotatable in the connector sleeve.

The lock flange or skirt 14 of the connector sleeve is formed -at its free end with a slot 20 and the socket portion 4 ot the terminal shell is also formed with a slot 21 adapted to register' with said slot in the flange 14. The insulating guard 1G is enlarged at its end surrounding the slotted portions of the sleeve and terminal shell and extending longitudinally inwardly through said enlarged end is a key opening 22 which opens adjacent its inner end into the interior of the guard 16. A key 23 is provided for locking the terminal shell and the connector sleeve tothe guard. This key is formed with an insulation handle 24 and a shank 25. The shank is formed with a recess 26 which opens through the side of the shank. 1A locking member 2T is pivoted in this recess the said member being formed with a locking head 28 at its free end. A spring 29 within the recess normally forces the free end of the locking member out of the recess so that the locking head 28 projects laterally from the shank of' the key. v The outward movement ofthe locking member is limited by a stop pin 30. The opposite lateral edges of the locking head converge outwardly to provide cam edges for a purpose to be presently described. The key is adapted to be inserted into the opening 22 in the guard 16 and through the slots 20 and 21 in connector sleeve and the terminal shell when they are in register in order to leek the three members of the device together against independent rotation and to permit them all to e rotated together.

The'lamp bulb is provided with the usual threaded terminal cap 31 of standard size, and this threaded cap is adapted to be screwed into the terminal socket 4. The

usual. terminal 32 of the lamp is adapted to engage the Contact 11 on the plug 3. One of the terminal wires of the lamp is connected to the Contact 32 and the other is connected to the threaded terminal cap. When the connector sleeve is screwed into the ordinary lamp socket or plug receptacle, the said sleeve is in electrical Contact with one of the terminals of the circuit and the contact 9 is in electrical engagement with the other terminal. As the connector sleeve is in electrical contact with the terminal shell and the contact 9 is through the cbiled spring 10 electrically connected with the contact 11, it is obvious that the lamp circuit will be completed in the usual way through the Contact 32 and theterminal cap 31.

When it is desired to screw the device into an ordinary threaded socket or a receptacle the key is inserted into the opening 22 in the guard, In inserting the keyinto the opening one ot' lthe cam edges of the outwardly projecting locking head 28 will come in contact with the edge of the opening and be cammed thereby, against the resistance of the spring 29, back into the recess 26 and within the compass of the shank of the key. The key may then be thrust to its innermost position. The parts ol the device are then rotated to bring the slots 20 and 21 into register with the key opening in the guard, whereupon the spring 29 will snap the locking headV outwardly of the key shank and through the said slots thus locking all of the rotatable parts together. The connector sleeve may then be screwed into the socket, and the lamp, or

.a similar threaded connector plug, may then be screwed into the terminal socket 4. T0 remove the key. the handle is simply given an outward pull causing the opposite cam Aedge of the locking head 28 to strike'the edge of the inner end of the key opening to cam the head 28 back out of the slots 20. and 21 and into the shank to provideelearance for the withdrawal of the key. The guard and the terminal socket are thereby freed so that they may rotate on the threaded connector sleeve. It is obvious that when `the key is removed the lamp cannot be unscrewed from the terminal socket, because said socket will freely rotate in'thc con- 'i nector sleeve. It is also obvious that the connector sleeve willnot be rotated because of itstrictional engagement with the threaded socket. The outer end of the threaded connector sleeve extends beyond the end o1 the-insulating plug 3, and has suitably mounted thereon a stop ring 33 that is adapted to limit the yinward movement of the connector sleeve into the socketv into which it is screwed. The contact 9 is normally thrust outwardly beyond the end of the stop ring 33 by the spring 10 so that `when Athe idevice isscrewed homelthe `said Contact `willpbe forced back against the re sistance ofthe spring and the spring will hold it tightly aga-inst` the lixed contact in the socket and a good electrical connection will be ensured. The yieldable contact 9 also adapts the plug to a socket of any construction. In order to prevent a short circuit between said lixed contact and the connector sleeve of the device, the stop is made of insulating material. When the connectorl sleeve is screwed tightly into a socket the annular edge of the ring 33, lirmly abutting the bottom of the socket, will prevent twisting or canting of the sleeve and, will frictionally resist the unscrewing of the sleeve and prevent its unauthorized removal by a manipulation of the other parts of the plug connector.

A fault that is very comlnon in devices of this character is that by means of canting or straining the lamp bulb to one side it? is possible to cause the socket to frictionally bind, 'in which case the lamp may be unscrewed from the socket without the use of a key. the present invention by making the connector sleeve 13 materially larger than the terminal shell 1 as shown in Fig. 1. It is then impossible to cause the terminal shelll to frictionall'y bind in the connector sleeve 13 by canting the lamp bulb. The flange 5 extends outwardly to touch the inner side walls of the guard 16 and prevent the socket 4 from being forced against the surrounding skirt 14. This renders it impossible tounscrew the plug by inserting the thumb into socket 4 after the lamp has been removed, and pressing the socket 4 against the skirt 14 to frictionally bind it thereto. It will be seen also that owing to the use of a key that is inserted in a direction longitudinally of the device through a small opening and expanded laterally after it is inserted, it is much more difficult to improvise a key that will lock the parts together than is the `case where a. standard key insertable laterally of the device is used.

The forming of the guard 16 with an enlarged portion provides a shoulder 34 that is adapted to support a lamp shade.

What I claim is: f

1. In a plug connector of the class set forth, a freely rotatable outer sleeve formed with a keyway extending longitudinally inward from the outer end of the sleeve and opening laterally into the interior of the sleeve at a point spaced from said end; and a laterally compressible and expandible key adapted to enter said keyway when compressed and to expand through said lateral opening in the keywa-y when inserted to eiect a locking connection with parts of the plug connector Within the sleeve.

This fault is overcome in` forth, a freely rotatable 'outer sleeve formed with` a keyway extending longitudinally inward from the outer end of the` sleeve and,

opening laterally into the interior of the sleeve `at a p oint spacedfrom said outer end; f

and a key adapted to vbe inserted into and removed from said keyway and formed with an insulation handle, a shank, and aspring-projected locking member normally extending laterally outward from said shank, the keyway being formed to receive the key only with the said locking member compressed and to permit the locking member to expand through its lateral opening into the sleeve when the key is `inserted to effect a locking engagement with parts of the plug connector within the sleeve.

3. In a plug connector of the class set forth, a freely rotatable outer sleeve formed with a keyway extending longitudinally inward from the outer end of the sleeve, said keyway being formed wit-h a restricted mouth and opening laterally into the interior of the sleeve at a point spaced inward from said mouth; and a removable key formed with an insulation handle, a shank, and a spring-projected locking member normally expanded laterally outward from said shank and adapted to be compressed inward, the restricted mouth of the keyway being formed to receive the shank of the key only with the locking member compressed, the lateral opening of the keyway being formed to permit the locking member to expand into the sleeve to effeet a locking connection with parts of the connector plug within the sleeve when the key is fully inserted, and the locking mem ber being formed with outwardly converging cam edges adapted respectively to engage the inner and outer edges of the restricted portion of the keyway and cause the member to be compressed thereby to pass through the restricted portion when the key is moved lony gitudinallyin either direction.

4. A plug connector comprising a holder for a terminal contact; an internally threaded lamp socket carried by the said holder and rigid with it; an externally threaded connector sleeve surrounding the holder and freely rotatable relatively to it; means forming an annular insulating abutment and friction edge rigidly carried by the connector and spaced outwardly from the end thereof to abut the bottom of a socket into which the connector sleeve is screwed; a compressible terminal contact carried by the said contact holder and compressible longitudinally thereof; a freely rotatable guard and operating sleeve surrounding the lamp socket; and means to temporarily lock the lamp socket and the connector sleeve to the operating sleeve to rotate with it.

5. A plug connector comprising a holder V4 l y1,675,353

for a terminal Contact; an externally threadsocket into which the connector sleeve is ed connector sleeve surrounding said holder screwed; and a spring projected terminal and freely rotatable relatively to it; insula- Contact carried by the said Contact holder 10 tion meansV forming an annular abutment and and compressible longitudinally thereof. l 5 friction edge rigidly carried by the connector In testimony whereof I hereunto ax my l sleeve and spaced outwardly from the end signature.

thereof to frctionally abut the bottom of u LOUIS KELLNER. 

